Automatic dimming and recycleable lamp

ABSTRACT

A sound responsive apparatus for automatically dimming a lamp from an initial condition of maximum brightness to a terminal condition of minimum brightness comprising a detector for detecting the presence of sound having at least a predetermined amplitude and an automatic dimming apparatus operatively connected to the detector to actuate the automatic dimming apparatus upon detecting sound having at least the predetermined amplitude. The automatic dimming apparatus, when actuated, controls the brightness of the lamp from a first level of brightness to a second, diminished, level of brightness. Means may be provided for varying the period of time required for the lamp to pass from maximum brightness to minimum brightness.

United States Patent 1191 Herbits 1451 Aug. 5, 1975 AUTOMATIC DIMMINGAND RECYCLEABLE LAMP [76] Inventor: Charles G. Herbits, 2400 VirginiaAve., N.W., Washington, DC.

[22] Filed: July 24, 1973 [21] Appl. No.: 382,279

[52] US. Cl. 179/1 VC; 315/291 [51] Int. Cl. H03k 17/56; HO4r 3/00 [58]Field of Search 179/1 VC, 1 VL; 340/148,

340/279; 181/5 Sl-l; ZOO/61.01, 33 R;

[56] References Cited UNITED STATES PATENTS 2,998,547 8/1961 Berman315/291 3,491,263 1/1970 Isaacs 315/307 Primary ExaminerKathleen H.Claffy Assistant E.\'aminerDouglas W. Olms Attorney, Agent, orFirmBurns, Doane, Swecker & Mathis 5 7 ABSTRACT A sound responsiveapparatus for automatically dimming a lamp from an initial condition ofmaximum brightness to a terminal condition of minimum brightnesscomprising a detector for detecting the presence of sound having atleast a predetermined amplitude and an automatic dimming apparatusoperatively connected to the detector to actuate the automatic dimmingapparatus upon detecting sound having at least the predeterminedamplitude. The automatic dimming apparatus, when actuated, controls thebrightness of the lamp from a first level of brightness to a second,diminished, level of brightness. Means may be provided for varying theperiod of time required for the 3,534,224 10/1970 Skirpan etal 315/2913,582,671 6/1971 Ott 340/148 lamp to pass from maximum brightness tominlmum 3,636,515 1/1972 Smith 340/148 brlghmess- 3,733,528 5/1973Gilbreath 315/291 4 Cl 2 D 3,748,496 7/1973 Hfidln et a] 179/1 vc 1raw'ng SUPPLY 1111 24 26 MIN POWER POWER i6 20 22, 1 32, 14

ELECTRONIC AUTOMATIC Dj DETECTOR SWITCH DIMMER SWITCH 111115511010EXTlNGUiSHING 1011151 ao AUDIO RATE OUTPUT PATENTED AUG 51975 SHEETAUTOMATIC DIMMING AND RECYCLEABLE LAMP BACKGROUND OF THE INVENTION Itis, therefore, a general object of the present inven- The presentinvention relates to a control apparatus 5 tion to provide an automaticlight dimming apparatus for varying the power available to a load inresponse to the presence of sound having at least a predeterminedamplitude. More particularly, the invention relates to an electric lampwhich is illuminated in response to the presence of sound above apreselected level and is then automatically dimmed.

It is a common problem with children, especially dur ing very earlyyears, to require some kind of attention during the night. Since manychildren are afraid of the dark, some form of continuously-on nightlight may be required to provide sufficient reassurance and to eliminatewhat otherwise might be discipline problems.

It is well known that many persons, including children, enjoy soundersleep in total darkness. Hence, many parents wait until their childrenfall asleep with some form of night light burning and quietly enter theroom to turn off the light. This may often prove to be a source of greatannoyance and inconvenience to the parents.

If such a child awakens during the night, he may cry if he discovers heis in darkness, and he may require that the night light be turned onagain before he will stop crying. Such sleeping habits may prove notonly annoying to the parents of such children but also may damage thephysical and mental health of the parents.

It has been found that a gradually dimming light will tend to relax andmake a person in the presence of such light sleepy. It has also beenfound that the sleep inducing effect of the gradually dimming light isparticularly effective with children.

In addition and of independent significance are timedelay switches whichare operable to provide a delay of a predetermined time period beforethe switching action is completed. Such devices permit, for example, aperson to operate a light switch, cross a room, and get into bed beforethe light is switched off. However, to turn on the light again, theperson may be required to walk across the dark room to reactivate theswitch with a risk of stumbling or falling in the dark room.

Devices exist in the prior art which activate lights in response tosound. Such devices provide increased power to a lamp in response torelatively loud sounds and reduced power to the lamp in response torelatively quiet sounds so that the light flickers in response to thevarying amplitude of the sound.

Other devices exist which activate a switch in response to the presenceof sound above a preselected threshold volume. Devices also exist in theprior art for dimming a light from a first level of intensity to asecond level of intensity.

However, the need continues to exist for a device which is suitable toautomatically activate a lamp to, say, provide assurance to childrenawakening in the night and thereafter provide a sleep inducing dimmingof the lamp over a preselected period of time in response to the childsneeds as evidenced by crying and the like.

It would therefore be desirable to provide an automatic, light dimmingapparatus which can be activated by sound above a predeterminedamplitude and which may be reset upon each subsequent reoccurrence ofthis preselected sound amplitude.

which minimizes or reduces the problems and shortcomings of the typepreviously noted.

It is a more particular object of the present invention to provide aslowly extinguishing light which may be sound actuated and which may besubsequently reset by sound.

It is another object of the present invention to provide an automaticresetting light dimming apparatus which may slowly extinguish a lightfrom a first predetermined brillance to a second predetermined brillanceand maintain the light at the second predetermined brillance.

It is yet a further object of the present invention to provide anautomatic, resetting light dimming apparatus which has a preselectedextinguishing rate.

It is yet a further object of the present invention to provide anautomatic, resetting light dimming apparatus which may be reset eitherduring a dimming cycle or after a dimming cycle has completed.

An automatic, resetting light dimming apparatus according to a preferredembodiment of the present invention intended to substantially accomplishthe foregoing objects includes a lamp, a detector for detecting thepresence of'sound having a predetermined amplitude, a dimmer forautomatically controlling the brightness of the lamp, when actuated,from a first level of brightness to a second, diminished level ofbrightness over a predetermined time period, means for providing powerto the lamp, and a switch which is responsive to the sound detector foractuating the dimmer in the presence of a predetermined amplitude ofsound. The apparatus may include means for varying the extinguishingrate of the lamp and may further include means for setting the initialand terminal intensities of the lamp. Moreover, means may be providedfor varying the minimum amplitude or threshold sound at which theapparatus is actuated.

BRIEF DESCRIPTION OF THE DRAWINGS Other objects and advantages of thepresent invention will become apparent with reference to the followingdetailed description of a preferred embodiment thereof in connectionwith the accompanying drawings wherein like reference numerals have beenapplied to like elements, in which:

FIG. 1 is a block diagram of the apparatus of the present invention; and

FIG. 2 is a schematic diagram of a preferred embodiment of the presentinvention.

In FIG. 1 there may be seen an automatic resetting dimming apparatus 10connected to a source 12 of alternating current. A microphone 14 isprovided which is connected to a detector stage 16. The microphone 14may be a conventional crystal microphone. The detector stage 16 isoperable to detect an audio signal having a predetermined amplitude. Theminimum amplitude to which the detector will be responsive may be presetby means of a threshold adjustment 18.

The detector 16 is connected to an electronic switch 20 which isactuated when the detector receives an audio signal above the presetthreshold amplitude. This electronic switch 20 is connected to anautomatic dimmer 22 and is operable to reset the automatic dimmer.

This automatic dimmer 22 may include a maximum adjustment 24 and aminimum adjustment 26. The maximum adjustment is generally preset to atleast provide the maximum illumination from the lamp 28 although, ifdesired, the maximum adjustment may be adjusted to a lesser value. Theminimum adjustment 26 is operable to set the minimum illumination atwhich the light 28 may be continuously maintained when the automaticdimmer 22 has cycled through its extinguishing period. Often, theminimum adjustment may be set at a value which gives substantially zeroillumination. In the preferred form of the invention, the automaticdimmer 22 is electronic and when triggered, will alternately charge anddischarge an RC circuit having an extremely long time constant as willbe described in greater detail below. In the alternative, the automaticdimmer 22 may include a conventional clock or similar timing mechanism(not shown) connected to a rheostat (also not shown).

The automatic dimmer 22 may include an adjustment 30 for adjusting theextinguishing rate which will determine the period required for thedimmer to pass from its initial maximum setting to its terminal minimumsetting.

The automatic dimmer 22 is connected to a switch 32. This switch 32controls the average power from the alternating current source 12 whichis applied to the light 28. In the preferred form of the invention, thisswitch may be a solid state electronic circuit which conducts currentfor a relatively long interval when the automatic dimmer is operating inthe maximum range of its cycle and for a relatively short interval whenthe automatic dimmer is operating in the minimum range of its cycle.

Thus, it can be seen that sound will be converted to an audio signal inthe detector. If the audio signal is of a sufficient amplitude to exceedthe threshold adjustment, the first switch will be actuated. When theswitch 20 is actuated, it triggers the automatic dimmer 22. Theautomatic dimmer in turn is connected to a second switch 32 and theautomatic dimmer and switch 32 together function to provide apredetermined maximum power to the light and then reduce the power to apredetermined minimum to thereby reduce or dim the illumination providedby the light 28. The automatic dimmer may be adjusted to vary the rateat which the maximum power falls to the minimum power. This period orextinguishing rate, may vary from several seconds to, a predeterminedtime of up to about 20 minutes.

The sound responsive apparatus of the present invention may alsooptionally include an audio output device 80 shown by dotted lines inFIG. 1 such as a tape player, cassette player, radio, television or thelike. The audio output device may be operative in conjunction with thesound responsive apparatus of the invention in any suitable conventionalmanner so that the device is energized when the lamp circuit is actuatedto the maximum brightness and is deen'ergized at the end of theextinguishing period. For example, the timing signal from the automaticdimmer 22 which controls the operation of the lamp 28 may control theon/off cycle of the audio output device in a suitable manner.Advantageously, the audio output device such as a tape or cassetteplayer can be pre-programmed to include soothing, sleep-inducinglullabies or sounds of barking dogs or the like depending upon thecontemplated use ofthe sound responsive apparatus.

In FIG. 2 there is illustrated a preferred embodimen of the invention indetailed schematic diagram form. Referring now to FIG. 2, an AC signalfrom the AC supply 12 may be applied to a direct current (DC) powersupply source 33 to provide the DC output voltage required for theoperation of the detector 16, electronic switch 20 and the automaticdimmer 22. The DC suppply 33 may be any suitable conventional AC/DCconvertor such as the illustrated full wave rectifier and may include aZenner diode 34 or other suitable voltage regulating means.

The detector 16 preferably includes a high impedance, low power inputtransistor 36 driven by the sound detector or microphone 14, and afurther amplifying transistor 38. The transistors 36 and 38 may beapplied from the DC power supply 33 through a suitably poled blockingdiode 40, and the detector 16 may be coupled from'the DC source throughthe use of a suitable decoupling capacitor 42. A biasing resistor 44 maybe provided between a gate electrode of the transistor 36 and common orground for the circuit, and load resistors 46 and 48 may be provided todevelop the output signals from the transistors 36 and 38. To provide anadjustment of the threshold at which the detector is energized, the loadresistor 46 may be a potentiometer so that a selectable percentage ofthe output signal from the transistor 36 may be coupled through thetransistor 38.

The electronic switch 20 preferably comprises a silicone controlledrectifier (SCR) 50 having its anode electrode connected to the source 33of DC voltage and having its cathode electrode connected through acontrol switch 52 and a variable RC timing circuit 54 to common. Theoutput signal from the detector 16, i.e., the output from the transistor38, may be applied to the gate electrode of the SCR 50 to control theconduction thereof.

The switch 52 may be a manually operable, three position switch havingan on position, an auto and an off position. In the auto position, thecharging of the RC timing circuit 54 may be controlled through selectivecontrol of the conduction of the SCR 52. In the on position of theswitch 52, the RC timing circuit is kept fully charged from the DCsource, and in the off position of the switch 52 the RC circuit 54 isfully discharged, i.e., is grounded.

The RC timing circuit 54 may be a part of the automatic dimmer 22 andthe time constant thereof may control the period of time over which thelamp 28 is dimmed from its maximum level to its minimum level. Tofacilitate the adjustment of this period of time or extinguishing rate,a variable resistor 56 may be pro vided to control the discharge time ofa capacitor 58 and to thereby control the RC time constant of the timingcircuit 54.

An output signal may be coupled from the timing circuit 54 throughbiasing resistors 60 and 62, through a variable biasing resistor 64, andthrough a switch 66 to the DC power supply output signal. The timingcircuit 54 output signal may be coupled from the resistor 60- resistor62 junction to the input terminal of a suitable amplifier such as theillustrated Darlington amplifier 68. The output signal from theamplifier 68 may be applied to the gate electrode of a conventionalunijunction transistor 70 and the gate electrode of the transistor 70may be supplied through a resistor 72 with a DC biasing voltage from theDC supply 33 and may be connected to ground through a capacitor 74. Theunijunction transistor 70, when rendered conductive, may generate asignal across the primary of a transformer 76 and the secondary windingof the transformer 76 may be connected to the gate electrode of asuitable switch 32 such as the illustrated TRIAC 78.

In operation, the switch 66 may be coupled to the adjustment knob of thevariable resistor 64 and may be closed when the variable 64 is increasedin resistance. The increase in resistance of the resistor 64 controlsthe minimum brightness of the lamp 28 as will hereinafter becomeapparent. To effect this terminal brightness adjustment, the switch 52may be placed in the auto position to engage the RC timing circuit 54.The variable resistor 56 may be set to a position of a relatively highextinguishing rate to bring the lamp 28 to its minimum brightness. Theresistor 64 may then be adjusted to set the brightness desired after thedimmer has passed through its extinguishing cycle.

Any sound detected by the microphone 14 is converted to an electricalsignal and applied to the gate electrode of the transistor 36. If theamplitude of the detected sound exceeds the threshold set by thepotentiometer 46, the transistor 38 is triggered rendering the SCR 50conductive. Conduction of the SCR 50 charges the capacitor 58 of the RCtiming circuit 54 and, as the charge on the capacitor 58 increases, theconduction of the Darlington amplifier 68 increases so that capacitor 74charges more rapidly.

The capacitor 74, the resistor 72 and the unijunction transistor 70 forma pulsing circuit which periodically gates the switch 32 to supply ACpower to the lamp 28. Prior to the triggering of the SCR 50, the periodof the oscillator is sufficiently long that very little AC power issupplied to the lamp 28 and the lamp 28 is quite dim. This minimum powerlevel is set by the variable resistor 64 since the resistor 64 controls,at least in part, a bias level supplied to the amplifier 68. When theSCR 50 conducts and the amplifier 68 charges the capacitor 74 morerapidly, the period of the oscillator or pulser formed by theunijunction transistor 70 increases considerably and the conductionperiod of the switch 32 is likewise increased considerably. The AC powersupply to the lamp 28 is thus increased to the predetermined maximumvalue.

When the SCR 50 is rendered nonconductive, the capacitor 58 dischargesin accordance-with a time constant determined primarily by the variableresistor 56. As the capacitor 58 discharges, the conduction of theDarlington amplifier 68 decreases and the charge time of the capacitor74 is thus increased. The period of the unijunction transistorcontrolled oscillator is thus slowly decreased resulting in the gradualdimming of the lamp 28. When the capacitor 58 reaches its initial chargecondition determined primarily by the resistor 64, the brightness of thelamp 28 is at its minimum or dimmed position. Of course, resistor 64 maybe adjusted to extinguish the lamp 28 at the minimum position.

The apparatus of this preferred form of the present invention maycomprise components having the following typical values:

Component Description Value 14' Microphone Crystal 34 Zenner Diode 24Volts, 1 Watt 36 Transistor N Channel Silicon FET 38 Transistor NPNSilicon Low to Medium Power, Beta Approximately 100 40 Diode l Amper.200 PN 42 Capacitor 50 Microfarads. 30 Volts 44 Resistor l Megohm 46Variable Resistor 5 Kilohms 48 Resistor l0 Kilohms 50 SCR 4500 Miliwatts56 Variable Resistor 5 Megohms 58 Capacitor I20 Microfarads. 30 Volts 60Resistor l Megohm 62 Resistor 2 Megohms 64 Variable Resistor 5 Megohms68 Two Transistors Each NPN Silicon Low to Medium Power. BetaApproximately 100 70 Transistor Silicon UJT, Approximately 300 Miliwatts72 Resistor l Megohm 74 Capacitor o.l Microfarad. 30 Volts 76Transformer Pulse 78 TRIAC SUMMARY OF ADVANTAGES AND SCOPE OF THEINVENTION It will be appreciated that in constructing the automatic,resetting light dimming apparatus according to the present invention,certain significant advantages are provided.

In particular, the present invention may be automatically set merely bysound above a predetermined amplitude. Once the apparatus has been setto the auto position, it is not necessary that the dimmer be manuallyreset for subsequent dimming cycles. The apparatus may be reset at anytime during the cycle by the presence of sound above the presetthreshold. The extinguishing rate may be varied depending upon theparticular use to which the present apparatus is put.

The present invention is operable to automatically dim a lamp to apredetermined minimum brightness so that dim light may be provided, say,throughout the night, but the light will be switched to full brillanceupon the detection of, say, a crying sound and will then gradually dimagain to the earlier level of minimum brightness. Whereas there are awide variety of applications in which the present invention may beadvantageous over known devices, the apparatus of the present inventionfinds particular utility in child care. Child care may be facilitatedthrough the use of the present invention to the advantage of parents.The apparatus of the present invention, furthermore, can be used toinduce sleep in persons who encounter difficulty in falling asleep. Thepresent apparatus also may advantageously be used to provide increasedsafety to a homeowner since the noise made by a potential burglar mayactuate the apparatus and scare off the burglar. Other advantageous useswill quickly come to mind.

Thus, it is apparent that there has been provided in accordance with theinvention an automatic resetting light dimming apparatus thatsubstantially satisfies the objects and advantages set forth above.Although the present invention has been described in conjunction withspecific embodiments thereof, it is evident that many alternatives,modifications, and variations will be apparent to those skilled in theart in light of the foregoing disclosure of the invention. Similarly,many of the components may be replaced by well known substitutions, ordevices not yet popularly known and even devices yet to be invented,which exhibit characteristics necessary for the operation of anapparatus in accordance with the present invention. Accordingly, it isintended that all such alternatives, modifications, and variations whichfall within the spirit and scope of the invention as defined in theappended claims be embraced thereby.

What is claimed is: 1. A sound responsive apparatus for automaticallycontrolling the brightness of a lamp, said apparatus comprising: a lamp;detector means for detecting the presence of sound having at least apredetermined amplitude;

dimming means for energizing said lamp at a first predetermined level ofbrightness, when actuated, and for automatically reducing the level ofbrightness of said lamp from said first level to a second predeterminedlevel of brightness lower than the first level over a predetermined timeperiod; and

switch means cooperable with said detector means for actuating saiddimming means in response to the detection of sound above thepredetermined amplitude.

2. The apparatus of claim 1 and further including:

threshold adjustment means for varying the minimum amplitude of sound atwhich said detector means will actuate said switch means.

3. The apparatus of claim 1 and further including:

variable adjustment means for varying a minimum brightness of said lampto prevent said dimming means from reducing the brightness of said lampto below a predetermined level.

4. The apparatus of claim 1 and further including:

variable dimming rate adjustment means for varying the time required forsaid dimming means to reduce the power available to said lamp from amaximum power level to a minimum power level.

5. The apparatus of claim 1 further including:

audio output means operatively connected to said switch means andactuated by said switch means in response to to said sound above thepredetermined amplitude.

6. A sound responsive apparatus for automatically reducing the power toa load from an initial condition of maximum power to a terminalcondition of minimum power, said apparatus comprising:

detector means for detecting the presence of sound having at least apredetermined amplitude; and means responsive to said detector means forproviding an initial condition of maximum power to the load and forreducing over a predetermined time period the power available to theload from said initial condition of maximum power to a terminalcondition of minimum power when said detector means detects sound havingthe predetermined amplitude. 7. The apparatus of claim 6 and furtherincluding: threshold adjustment means for varying the minimum amplitudeof sound at which said automatic power reducing means will respond tosaid detector means. 8. The apparatus of claim 6 and further including:varible power reducing rate adjustment means for varying the period oftime for said automatic power reducing means to reduce the power to saidload from the maximum condition to the minimum condition. 9. Theapparatus of claim 6 wherein the load is a lamp.

10. A sound responsive apparatus for automatically dimming a lamp, saidapparatus comprising:

detector means for detecting sound having at least a predeterminedamplitude; first electronic switch means operably responsive to saiddetector means when sound having an amplitude at least as great as thepredetermined amplitude is detected; second electronic switch meansoperable to control the average power available to the lamp; automaticdimming means actuable by said first electronic switch means foractuating said second electronic switch means to provide a maximum powerlevel to the lamp and to reduce the average power available to the lampfrom said maximum power level to a minimum power level to therebyautomatically dim the lamp over a predetermined period of time whensound having at least the predetermined amplitude is detected; and meansfor supplying power to said detector means, said first and secondelectronic switches, and said automatic dimming means. 11. The apparatusof claim 10 and further including: threshold adjustment means forvarying minimum amplitude of sound at which said detector means willactuate said first electronic switch. 12. The apparatus of claim 10 andfurther including: variable adjustment means for varying a minimum poweravailable to the lamp to prevent said automatic dimming means fromreducing the power available to the lamp to below a predetermined level.13. The apparatus of claim 10 and further including: variable dimmingrate adjustment means for varying the period of time required for saiddimming means to reduce the power available to the lamp from the maximumpower level to the minimum power level. 14. The apparatus of claim 10further including: audio output means operatively connected to saidswitch means and actuated by said switch means in response to said soundabove the predetermined amplitude.

1. A sound responsive apparatus for automatically controlling thebrightness of a lamp, said apparatus comprising: a lamp; detector meansfor detecting the presence of sound having at least a predeterminedamplitude; dimming means for energizing said lamp at a firstpredetermined level of brightness, when actuated, and for automaticallyreducing the level of brightness of said lamp from said first level to asecond predetermined level of brightness lower than the first level overa predetermined time period; and switch means cooperable with saiddetector means for actuating said dimming means in response to thedetection of sound above the predetermined amplitude.
 2. The apparatusof claim 1 and further including: threshold adjustment means for varyingthe minimum amplitude of sound at which said detector means will actuatesaid switch means.
 3. The apparatus of claim 1 and further including:variable adjustment means for varying a minimum brightness of said lampto prevent said dimming means from reducing the brightness of said lampto below a predetermined level.
 4. The apparatus of claim 1 and furtherincluding: variable dimming rate adjustment means for varying the timerequired for said dimming means to reduce the power available to saidlamp from a maximum power level to a minimum power level.
 5. Theapparatus of claim 1 further including: audio output means operativelyconnected to said switch means and actuated by said switch means inresponse to to said sound above the predetermined amplitude.
 6. A soundresponsive apparatus for automatically reducing the power to a load froman initial condition of maximum power to a terminal condition of minimumpower, said apparatus comprising: detector means for detecting thepresence of sound having at least a predetermined amplitude; and meansresponsive to said detector means for providing an initial condition ofmaximum power to the load and for reducing over a predetermined timeperiod the power available to the load from said initial condition ofmaximum power to a terminal condition of minimum power when saiddetector means detects sound having the predetermined amplitude.
 7. TheappAratus of claim 6 and further including: threshold adjustment meansfor varying the minimum amplitude of sound at which said automatic powerreducing means will respond to said detector means.
 8. The apparatus ofclaim 6 and further including: varible power reducing rate adjustmentmeans for varying the period of time for said automatic power reducingmeans to reduce the power to said load from the maximum condition to theminimum condition.
 9. The apparatus of claim 6 wherein the load is alamp.
 10. A sound responsive apparatus for automatically dimming a lamp,said apparatus comprising: detector means for detecting sound having atleast a predetermined amplitude; first electronic switch means operablyresponsive to said detector means when sound having an amplitude atleast as great as the predetermined amplitude is detected; secondelectronic switch means operable to control the average power availableto the lamp; automatic dimming means actuable by said first electronicswitch means for actuating said second electronic switch means toprovide a maximum power level to the lamp and to reduce the averagepower available to the lamp from said maximum power level to a minimumpower level to thereby automatically dim the lamp over a predeterminedperiod of time when sound having at least the predetermined amplitude isdetected; and means for supplying power to said detector means, saidfirst and second electronic switches, and said automatic dimming means.11. The apparatus of claim 10 and further including: thresholdadjustment means for varying minimum amplitude of sound at which saiddetector means will actuate said first electronic switch.
 12. Theapparatus of claim 10 and further including: variable adjustment meansfor varying a minimum power available to the lamp to prevent saidautomatic dimming means from reducing the power available to the lamp tobelow a predetermined level.
 13. The apparatus of claim 10 and furtherincluding: variable dimming rate adjustment means for varying the periodof time required for said dimming means to reduce the power available tothe lamp from the maximum power level to the minimum power level. 14.The apparatus of claim 10 further including: audio output meansoperatively connected to said switch means and actuated by said switchmeans in response to said sound above the predetermined amplitude.